1. Field of the Invention
The present invention relates to a pressure wave machine.
2. Discussion of Background
When pressure wave machines are used as the high pressure compressor stage of a gas turbine, precompressed air is further compressed in them in order to generate driving gas for the high pressure turbine part. The further compression of the air then takes place in a rotor whose periphery usually has cells which run parallel to the axis and in which the air comes directly into contact, without a solid separating element, with driving gas branched off from the turbine chamber. In order to control the inlets and outlets of air and gas into or out of the cells, casings with ducts for the supply and/or removal of the two media taking part in the pressure wave process are located at the two end surfaces of the rotor.
If a cell filled with air to be compressed passes in front of a high pressure gas inlet, a pressure wave propagates into the cell and compresses the air. The pressure wave reaches the end of the cell as soon as the latter passes the high pressure air outlet. The air is expelled there and the cell is then completely filled with gas. During further rotation, expansion waves ensure that the gas leaves the cell again and that fresh air is ced, whereupon the compression process is repeated. In contrast to the stationary casings, a radial pressure gradient forms in the cells of the moving rotor because of its rotation. In the vicinity of the ends of the cells and the connecting casings, a balancing flow appears, due to the different radial pressure gradients. This means that the fluid is accelerated at the outside of the rotor when flowing out of the rotor and is retarded at the inside of the rotor, or separation and reverse flow may even occur. When entering the cell, the flow is accelerated on the inside of the rotor and is retarded on the outside. It is generally known that strongly distorted velocity profiles have a direct effect on the efficiency and therefore make it worse. In addition, the blockage at the inlets and outlets greatly reduces the power density of a pressure wave machine.